Cam-controlled switch



y 1954 F. BAUER CAM-CONTROLLED SWITCH Filed Dec. 19, 1951 INVENTOR. FRANZ BA UEE BY 2 j n 77MB! A TTORNE Patented July 20, 1954 CAM-CONTROLLEDSWITCH Franz Bauer, Vienna, Austria, assignor to E lubert Naimer,Vienna, Austria Application December 1. 3, 1951, Serial No. 271,988

Claims priority, application Austria January 2, 1951 '7 Claims. 1

The present invention relates to an electric switch, which has acam-operated contact bridge the spacing of which relative to the switchaxis is changed upon performance of the switching movement, switchhaving arranged between the control cam and the contact bridge a rollerfollowing the control cam. It is an object of the invention to improvesaid switch so that its space requirement is reduced in relation to thepower to be controlled and a reliable double break is ensured even afterprolonged use, in spite of simplicity in structure and manufacture,desired combination being possible by aligning several of such switchesto perform any switching program.

The most varying types of cam switches that may be combined are known.Usually the individual switch contacts are operated by the switchingcams through the intermediary of rollers and levers, which are therebyswung about their pivots. These switches, however, interrupt the circuitonly at one point.

The attempt to use instead of the switching lever a double-breakingcontact bridge, which offers also the advantage or eliminating in thecircuit any flexible conductor involving various dimculties in the caseof high currents, has had only unsatisfactory results so far. Above allit has not yet been possible to derive in a simple manner from therotary movement of the cam the lifting movement of the contact bridge insuch a manner that even in continuous operation the contact bridge ismoved only in the direction of switching. As a rule this movement is tobe effected at right angles to the contact surfaces because then theabrasive wear of the contacts, which occurs upon sliding movementstransverse to the direction of switching and is dangerous particularlyfor silver contact surfaces, is eliminated. Whereas it is possible toavoid sliding contact movements and to achieve a simultaneous doublebreak if the parts guiding the contact bridge are manufacturedaccurately, in the known switches larger forces transverse to thedirection of switching are efiective in the contact bridge so thatsliding movements take place already when the components have been wornto a small degree only.

It is known to guide in a slot of the switch body the roller rolling onthe control cam, by means of an extension of the roller spindle, whichstands out from the contact bridge. The roller being mounted in thebridge in a direction normal thereto, the shear forces occurring duringthe operation of the switch and effective trans- Versely to theswitching movement are trans- 2 mitted to the contact bridge so that thedisadvantages just mentioned become apparent to an increasing extent asthe play between the guide parts increases.

It is also known to guide the contact bridge directly at the switch bodyand to arrange the roller connecting the control cam and the contactbridge in the switch body in a recess extending in the direction of theswitching movement. Since it is not possible to make the guide surfacesof the contact bridge long enough Without inadmissibly enlarging theswitch, this case also involves a wear of the guide surfaces by thelateral shear force occurring between the roller, which rotates uponswitching, and the contact bridge, so that an inaccurate, slidingcontact movement results.

Thus a permanently reliable guidance of the contact bridge, being arequisite condition for a simultaneous break of the contacts, involvesexcessively large switch bodies or, as is apparent from the switchstructure shown in the U. S. Patent No. 2,3083%, leads to switches inwhich the spacing of the contact bridge from the switch axis is notaltered during the switching movement. That type of switch is notsufficiently adapted for use in combinations and, moreover, is too largerelative to the power controllable thereby.

It is an object of the invention to provide a cam-controlled switch, inwhich the forces between cam, roller, and bridge are taken up in such amanner that a reliable double break is ensured even after a practicallyunlimited number of switch operations. This object is to be achievedwith small space requirements and simple structural elements.

To this end it is a feature of the invention to provide an electricswitch comprising at least one switch body member, a rotary cam, acontact bridge unit movable in a direction of switching to vary itsspacing from the axis of rotation of the cam, a roller interposedbetween the cam and the contact bridge unit and adapted to roll on thecam, a spindle for mounting said roller, said spindle having a diametersmaller than the roller, and mutually parallel projections provided onsaid switch body members and adapted to guide said spindle in saiddirection of switching and to prevent its movement transverse to saiddirection, said spindle engaging with said contact bridge unit only insaid direction of switching so that of a force exercised on the contactbridge unit only a component eirective in said direction of switching istransmitted, if insignificant sliding resistance forces are neglected.Thus, in accordance with the invention, the forces which are directedtransversely to the direction of switching and for the perfectabsorption of which long plunger guides were required previously, arederived exclusively to the switch body by a special bearing arrangementof the roller. This arrangement also permiis of a simpler mounting ofthe stationary contacts whereby, as a whole, the structure of thepresent switch is greatly simplified without affecting its eiiectivenessor service life.

Further features of the invention will be explained hereinafter withreference to the accompanying diagrammatic drawings, in whi h:

Fig. l is a top plan View on the switch body, showing the switchmechanism, the casing cover being removed, and

Fig. 2 a cross-sectional view of a switch combination consisting of twosuch switches and a stepping unit.

In Fig. 1 some of the movable parts and a stationary contact carryingconnecting part have been omitted whereas Fig. 2 shows the switch partmin a section taken along line IlIa:lIa, and the switch part b in asection along line IIbIIb of Fig. 1. Part 0 of Fig. 2 is the steppingunit common to both switches and not iorrning part of the invention.

Fig. 3 serves to explain the kinematic phenomena in the guide device forthe switch roller,

Figs. 4: to 6 show the construction of a stationary contact part, and

Figs. 7 and 8 show the construction of the contact bridge.

The insulating switch body I is suitably formed from synthetic resin. Ithas four apertures, through which the clamping studs :2 are stuck, whichas shown in Fig. 2 hold together the entire combination switchconsisting in the present eX- ample of the switch units a, o and thestepping unit 0. The square switch shaft 3 carries the switching cams 5,each of which cooperates with pressure rollers 5only the upper one isshownof the switch plunger. In Fig. 1 the switching cam i is indicatedwith dashed lines. Each switch plunger consists of a pressedsyntheticresin part i into which a roller-guiding metal fork 8 ispressed, in which the spindle 9 carrying the roller 5 is mounted. Asshown on Fig. 2, this part "i is guided between a smooth part of theinside wall it of the switch body member I, on the one hand, and asimilar part of the outside wall i2, which may form part of the adjacentswitch body member or, as in the example shown, of a cover member Thecontact bridge it rests with a large surface area on the outer end faceof the part i. For its safe fixation on the part l the contact bridgehas an aperture embracing an extension I? or" the part 1. A compressionspring !8 bearing against the rim part is of the switch body member I,acts directly on the contact bridge l5.

As may be seen from the upper part of Fig. 2a, the spindle s of theroller laterally protrudes beyond the prongs or the fork 8. Theseprotruding parts find safe guidance on the one hand in a slot atrecessed into the switch body member I and forming a guiding groove, andon the other hand i a guide piece 2! resting in a recess 22 in thecasing cover 3'5 (Fig. 2). For the assembly of a combination switch theoutside of the switch body member is given corresponding recesses 22,into which the guide pieces of any adjacent switch unit are inserted.

The embodiment shown illustrates a double switch having two mutuallyopposite contact bridges l5, that a switch for the simultaneousinterruption of two conductors. The invention is not restricted to thistype of switch; it is possible to interrupt at the same time three ormore circuits, the contact bridges being suitably providcd in a stararrangement. By a corresponding shape of the switching earn it ispossible to cause one circuit to be closed when the other is opened,etc. Moreover, it is apparent from Fig. 2 that by arranging any desirednumber of switch bodies in am'al alignment, and operating them by asingle shaft 5, any desired switching program may be performed. Toensure that any switch combination may be assembled from prefabricatedparts, the necessary stepping mechanism is provided in the form or" aseparate stepping device 0 (Fig. 2).

By a turning of the switch shaft 3 the can wheel l is turned whereby theswitch plungers by means of the roller 5, its spindle 8 and forks 8, arelifted, or, if they had been lifted, are lowered by the rollers 5falling under the action of the spring is into the recesses on thecamwheel. The kinematic phenomena occurring during these operations willnow be explained with reference to Fig. 3, in which like referencenumbers as in Figs. 1, 2 are used for like parts.

The spindle 9 has in the fork 3 some lateral play, which relative to theplay of said spindle in the guide slot as or slot plate 2| is so chosenthat upon a turning of the cam i and the resulting lateral displacementof the roller 5 the spindle 9 will contact the respective side faces ofsaid guide grooves (indicated at 2i) in Fig. 2 and registering inprojection with the corresponding side faces of the slide pieces 2!) butdoes not contact the side faces 3 of the prongs oi the fork. When it isassumed that the cam be turned in the direction of the arrow A, theroller 5, when lifted by the cam surfaces i, will be displaced somewhatto the right, whereby the spindle e of the roller contacts theright-hand surfaces 26 of the guide groove 26 or of the slide piece 2i(compare also Fig. 1). Gwing to the special manner in which the spindle9 cooperates with the fork 8, essentially thereby that the spindle hasin the fork more lateral play than the guide grooves 26, 2 2, whereas onthe other hand the surface 8 of the fork rests on the spindle 9, therequirement is fulfilled that the spindle 9 is operatively connectedwith the contact bridge l5 practically only in the direction ofswitching B (Fig. 3) by way of the parts I and 3. Thus of any forcesexercised by the spindle 9 on the forks 8 only the components extendingin the direction of switching are transmitted, whereas the componentsextending transversely to the direction of switching are absorbed by theguide means 2e, 2!. Thus the guide means provided in the switch body forthe plungers I remain practically free from lateral stresses and,therefore, are hardly worn, whereas in the known types such wear soonresults because in switches of such type surface lubrication to remedysuch wear is not applicable, as a rule. Since theseguide means in thepresent case are subjected to small stresses only, they may be short ormay under certain circumstances be eliminated entirely.

During the lifting of the roller 5 by the camthe former turns in thesense of the arrow 0, whereas the spindle 9 rolls on 242' and S",turning in the sense of the arrow D, that is, in

,for the spindle 9.

the opposite sense as the roller 5. It is apparent that sliding frictionis exercised to any substantial extent only between the roller 5 and itsspindle ii; the thus produced lateral shear effeet is small, however,and be removed almost entirely if antifriction bearings are used Theroller 5 being of much larger diameter than the spindle 9, both partsmay be made integral, without thereby substantially deteriorating theconditions described because the fact that parts 5 and 9 are integraldoes not substantially affect the described resolution of forces.

As a result of being operated in this special manner, the contact bridgeis lifted accurately from the fixed contacts provided on contact piecesor connecting pieces 25. This lifting taking place evenly and withoutsliding movements between the contacts, the latter have a silver layerwithout any risk that the contact may be worn off soon.

Since by the described operation of the contact bridge the contact ismade without a lateral stressing of the connecting parts 26 carrying thestationary contacts, the same need not be fixed to the switch body byscrews.

In the embodiment shown the parts 26 are inserted with their ends intorecesses 36 of the switch body. Moreover, the parts 25, as shown inFigs. 4 and 5, which represent the contactcarrying stationary connectingpart in a front view (Fig. 4) and an appertaining side elevation (Fig.5), have extensions 3| which also fit into corresponding recesses 32 ofthe switch body (shown at bottom right in Fig. 1, where the connectingpart has been omitted). The extensions of the part 26 (Figs. 4, 5) fitcorresponding recesses provided at the outside of the adjacent switchbody member I (Fig. 2b) or of a cover part 3'! (Fig. 2a). Thisconnecting part is formed by bending from a flat copper strip shown inFig. 6. The threaded holes receiving the terminal screws (see Fig. 1,top left) are designated with 34, the rivet hole to receive the contacthead 25 is designated with 35. The thus completed connecting parts arestuck without any fixing screws simply between the recesses provided onthe switch body or cover part 3'! and are clamped by the clamping screws2 forcing the said parts together.

Figs. 7 and 8 show a contact bridge in elevation and in a section takenalong line VII--Vl1 of Fig. 8, respectively, the contact heads beingomitted. An offset central portion 36 forms a spring plate for thecompression spring [8, the force of which determines the contactpressure.

The described bearing and guiding arrangement for the switch plungerpermits of numerous variations, of course, e. g., the guide piece 2| mabe eliminated entirely or may be provided at both ends of the spindle 9.

It may be said that by the construction according to the invention theforces transmitted by the cam to the roller are resolved into atransverse component, which is taken up only by the switch body orswitch casing, and a component moving the contact bridge. Since theforces laterally stressing the contact bridge are now eliminated, shortguide means for the same suifice so that the overall height is reduced.Because there are no longer any appreciable shear forces acting on thestationary contacts, either, the latter may simply be stuck into theswitch body, whereby the cost of manufacturing the switch is out. It maybe mentioned that the cam control described 6 may also be used as astepping mechanism in the part c, Fig. 2. In this case the contactbridge is eliminated. As compared with the prior art this arrangementleads to the replacement of the previously used tension springswhichtend to suffer eye breakage-by compression springs, and also savesspace.

I claim:

1. An electric switch comprising at least two switch body members,fixedly arranged contact parts carried by at least one of said switchbody members, said switch body members including a switch cover, arotary cam mounted in each switch body member, a contact bridge unitmovable in a direction of switching to vary its spacing from the axis ofrotation of the cam, and being adapted to cooperate with said fixedlyarranged contact parts, a roller interposed between the cam and thecontact bridge unit and adapted to roll on the cam, a spindle formounting said roller, said spindle having a diameter smaller than theroller, and mutually parallel projections provided on said switch bodymembers, one end or said spindle being mounted in the space between oneset of said projections provided on said switch cover, another end ofsaid spindle being mounted in the space between one set of saidprojections provided on another one of said switch body members, saidprojections being adapted to guide said spindle in said direction ofswitching and to prevent its movement transverse to said direction, saidspindle engaging with the contact bridge unit only in said direction ofswitching so that of a force exercised on the contact bridge unit only acomponent effective in said direction of Witching is transmitted.

2. A switch as set forth in claim 1, in which at least part of saidprojections are formed on an intermediate piece connected with therespective switch body member.

3. An electric switch comprising at least two switch body members,fixedly arranged contact parts carried by said switch body members, saidswitch body members including a switch cover, a rotary cam mounted ineach switch body member, a contact bridge unit movable in a direction ofswitching to vary its spacing from the axis of rotation of the cam, andbeing adapted to cooperate with said fixedly arranged contact parts, aroller interposed between the cam and the contact bridge unit andadapted to roll on the cam, a spindle for mounting said roller, saidspindle having a diameter smaller than the roller, and mutually parallelprojections provided on said switch body members, one end of saidspindle being mounted in the space between one set of said projectionsprovided on said switch cover, another end of said spindle being mountedin the space between one set of said projections provided on another oneof said switch body members, said projections being adapted to guidesaid spindle in said direction of switching and to prevent its movementtransverse to said direction, said spindle engaging with the contactbridge unit onl in said direction of switching so that of a forceexercised on the contact bridge unit only a component effective in saiddirection of switching, at least part of said projections being formedon a guide piece fixedly mounted in a recess of one of said switch bodymembers.

4. An electric switch comprising at least one switch body member, arotary cam, a contact bridge unit movable in a direction of switching tovary its spacing from the axis of rotation of the cam, said contactbridge unit having a forklike extension, a roller interposed between thecam and the contact bridge unit and adapted to roll on the cam, aspindle having a diameter smaller than said roller, said roller beingfreely rotatably mounted on said spindle, and mutually parallelprojections provided on each switch body member and adapted to guidesaid spindle in said direction of switching and to prevent its movementtransverse to said direction, said spindle extending through saidforklike extension with a lateral play larger than its lateral play insaid projections, said spindle engaging with the contact bridge unitonly in said direction of switch ing so that of a force exercised on thecontact bridge unit only a co: pcnent effective in said direction ofswitch is transmitted.

5. An electric switch comprising at least one switch body member, arotary earn, a contact bridge unit movable in a direction of switchingto vary its spacing from the axis of rotation of the cam, a rollerinterposed between the cam and the contact bridge unit and adapted toroll on the cam, a spindle for mounting said roller, said spindle havinga diameter small r than the roller, mutually parallel projectionsprovided on each switch body member and adapted to guide said spindle insaid direction of switching and to prevent its movement transverse tosaid direction, said spindle engaging with the contact bridge unit onlyin said direction of witching so that of a force exercised on thecontact bridge unit only a component effective in said direction ofswitching is transmitted, and connecting members carrying contactsadapted to cooperate with said contact bridge unit, each connectingmember having projections fixed to said switch body members only by theinterlocking of projections of each connecting member with recesses insaid switch body members.

6. In an electric switch comprising at least one switch body member: theprovision of means for transmitting motion only in a direction ofswitching from a rotary cam to a contact bridge unit movable in saiddirection of switching to vary its spacing from the axis of rotation oithe cam, said means comprising a roller interposed between the cam andthe contact bridge unit and adapted to roll on the earn, a spindle formounting said roller, said spindle having a diameter smaller than saidroller, a forklike extension of said contact bridge unit, and mutuallyparallel projections provided on each switch body member and adapted toguide said spindle in said direction of switching and to prevent itsmovement transverse to said direction, said spindle extending throughsaid forklike extension with a lateral play larger than its lateral playin said projections, said spindle engaging with the contact bridge unitonly in said direction of switching so that of a force exercised on thecontact bridge unit only a component eiTective in said direction ofswitching is transmitted.

'7. In an electric switch comprising at least one switch body member, arotary cam, a contact bridge unit movable in a direction of switching tovary its spacing from the axis of rotation of the cam, a rollerinterposed between the cam and the contact bridge unit and adapted toroll on the cam, and a spindle for mounting said roller, said spindlehaving a diameter smaller than the roller: the provision of means totransmit to the contact bridge unit, of a force exercised on saidspindle, only a component effective in said direction of switching, saidmeans comprising a forklike extension of said contact bridge unit andmutually parallel extensions provided on each switch body member andadapted to guide said spindle in said direction of switching and toprevent its movement transversely to said direction, said iorklikeextension embracing said spindle with a lateral play larger than thelateral play with which said projections embrace said spindle to preventsaid spindle from engaging with said contact bridge unit other than insaid direction of switching.

References Gited in the file of this patent UNITED STATES PATENTS NumberName Date 1,826,509 Douglas Oct. 31, 1931 2,308,406 Van Valkenburg Jan.12, 1943 2,511,821 Bullard June 13, 1950 2,588,632 Jefirey Mar. 11, 1952FOREIGN PATENTS Number Country Date 49,444 Netherlands Oct. 15, 1940228,328 Switzerland Nov. 15, 1943 633,808 Great Britain Dec. 30, 1949

